Normal vision requires rapid eye movements, known as saccades, to shift gaze to objects of interest. Although much is understood about the final stages of saccade generation within the brainstem, we know very little about how the brain decides when to shift gaze. Thus, the long-term goal of this work is to identify the neural circuits and computations responsible for regulating the initiation of gaze shifts. The proposed experiments will study the role of the frontal eye fields (FEF) and supplementary eye fields (SEF) in regulating saccade initiation in macaque monkeys (Macaca mulatta); both FEF and SEF are known to be involved in the generation of goal-directed saccades. Neural correlates of the regulatory processes will be identified using a novel behavioral method, known as the countermanding task, that systematically manipulates saccade production. In this task, a movement prepared in response to one stimulus must be inhibited if another delayed stimulus occurs. Neuronal discharges will be analyzed using novel techniques that quantify the magnitude and timecourse of neuronal modulation in relation to specific measures of behavioral performance derived from a race model. The strength of this proposal lies in the simultaneous assessment of visuomotor behavior and the activity of neurons that are involved in the production of the behavior. Also, guided by a specific model of behavioral initiation and inhibition, hypotheses linking brain and behavior will be developed by determining measures of neural activity that are effective predictors of behavioral performance. Successful completion of these experiments will provide significant new insights into the decision processes that culminate in saccade generation. Such information is necessary to more effectively diagnose and ultimately treat gaze disorders.